fdo#70465 SvTreeListBox::GetLevelChildCount refactored

Instead of iterating siblings returning count of parents child vector.
This slightly improves loading performance of "Expert Config" when accessibility enabled.

Change-Id: Ide1af3df19efaae9c0cc92086456bf3520ee5dd2
Honor selected device detection settings.

This fixes the problem of the software interpreter always getting selected
after initial startup where the settings are read from user configuration.

Change-Id: Iecbb7ae644c1264811f5280e1425a8dd776c2c1a
It performs better to use unordered_map than std::map here.

Change-Id: I5b89ac2dfbe348f0bf0b07880ccddc734b6d14ab